Automated Transmission Synchronization for Reverse Rolling
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Solution Overview
Problem
Automated transmissions without an electrical machine face challenges in synchronizing gear shifts during significant inclines or off-road conditions, leading to potential vehicle stalling or reverse rolling due to interrupted tractive power, and result in undesirable switching noises or gear rejection, impacting shift quality.
Innovation Solution
A method that synchronizes transmission input and output speeds by reducing the transmission input speed to a minimum when a direction change is detected, using existing components like the transmission brake or internal combustion engine, and employing a positive-locking shifting element to compensate for speed differences, allowing gear shifting without an additional electrical machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electrical machine is used to delay and accelerate the transmission input during synchronization, then the synchronous operation can be carried out in difficult shifting processes, but the device complexity increases and energy consumption increases
Solution Approach 1:
The transmission brake and internal combustion engine are used to reduce the transmission input speed to a minimum and compensate for speed differences during synchronization, eliminating the need for an additional electrical machine. The existing components serve the dual purpose of their original function and speed synchronization.
Solution Approach 2:
The transmission brake and internal combustion engine are employed for multiple functions: the brake is used for both stopping the vehicle and reducing transmission input speed during synchronization, while the engine provides both propulsion and speed compensation during the shifting process.
2Productivity
If the target speed is set independently of the direction of rotation, then the shifting process can proceed, but undesired switching noises occur and the switching claw may be rejected
Solution Approach 1:
The control unit continuously monitors the actual direction of rotation of the transmission input and compares it with the expected direction. Based on this feedback, the control unit adjusts the target speed setting and synchronization process to account for reverse rolling conditions, preventing switching noises and claw rejection.
Solution Approach 2:
The direction of rotation is detected before or during the shifting process, allowing the control unit to prepare appropriate countermeasures in advance. If reverse rolling is detected, the transmission input speed is reduced to a minimum and then accelerated against the rotation direction before the actual gear engagement, ensuring smooth synchronization.
3Device complexity
If the transmission input speed is reduced to a minimum using the transmission brake or internal combustion engine, then the synchronous process can be carried out without an electrical machine, but the shifting time increases
Solution Approach 1:
The synchronization process uses periodic acceleration and deceleration phases. The transmission brake is applied intermittently to reduce speed to minimum, then the internal combustion engine accelerates the input shaft, creating a rhythmic pattern of speed adjustment that achieves synchronization while minimizing total shifting time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables synchronous gear shifting between transmission input and output with different rotation directions, preventing vehicle stalling and reducing unwanted noises, while maintaining acceptable shift times and quality, even in challenging conditions, by determining and managing speed differences within mechanical limits.
Implementation Method 1
the transmission input speed can be reduced, for example, with an existing transmission brake
Implementation Method 2
the remaining speed difference between the transmission input speed and the output-side speed can be at least substantially synchronized or compensated for by the positive-locking shifting element of the transmission
Data Source
AI summary
A method for carrying out a gear shifting operation in an automated transmission with at least one vehicle transmission part shifting in an interlocking manner is proposed, in which, in order to shift a target gear (GTARGET), a synchronization of the rotational speed between the transmission input rotational speed and rotational speed on the output side is carried out, wherein, when a different direction of rotation between the transmission input and the transmission output is identified, the transmission input rotational speed is reduced to a minimum, and wherein the target gear (GTARGET) is shifted only if the remaining differential rotational speed between the transmission input rotational speed and the rotational speed on the output side can be at least substantially synchronized by the interlocking gearshifting element.